It has been well known so far that a silver halide color photographic light-sensitive material is exposed imagewise to light and color-developed so as to couple the oxidized product of an aromatic primary amine color developing agent with a color forming agent and, thereby, a dye including, for example, indophenol, indoaniline, indamine, azomethine, phenoxazine, phenazine or the like is formed, so that a dye image can be formed
The couplers for forming a yellow dye image include, for example, an acylacetanilide type coupler. The couplers for forming a magenta dye image include, for example, those of the pyrazolone type, pyrazolobenzimidazole type, pyrazolotriazole type or indazolone type. Further, the couplers for forming a cyan dye image include, for example, those of the phenol type or naphthol type.
Particularly, the couplers popularly used for forming magenta dye images include, for example, 1,2-pyrazolo-5-one couplers. The dyes formed of this type of couplers have a principal absorption in around 550 nm and, besides, a side absorption in around 430 nm. This type of couplers have had a serious problem from the viewpoint of color reproducibility, due to a color contamination caused by this side absorption of yellow component.
Further, in the case of the magenta couplers, yellow stains caused by light, heat and moisture in a color developed area are much more serious than in the cases of cyan and yellow couplers, so that the magenta couplers have had a defect in improving image preservability.
The particularly excellent magenta couplers, which have effectively improved the yellow stains as well as the above-mentioned side absorption being yellow component, include, for example, the couplers of the pyrazolotriazole type and the like types such as those described in U.S. Pat. No. 3,725,067, Japanese Patent Publication Open to Public Inspection (hereinafter referred to as Japanese Patent O.P.I. Publication) Nos. 99437-1984, 162548-1984 and 171956-1984, Research Disclosure Nos. 24220, 24230 and 24531, and so forth.
In the dyes formed of the magenta couplers such as those of the pyrazolotriazole type and so forth, the side absorption thereof around 430 nm is less by far than those of the dyes formed of the above-mentioned 1,2-pyrazolo 5-ones couplers. Therefore, they have excellent characteristics such as an excellent color reproducibility and very rare yellow stain produced by light, heat or moisture in the areas where no color is developed.
The dyes formed of the magenta couplers, such as those of the above-mentioned pyrazolotriazole type and so forth, have the excellent characteristics as mentioned above and they can satisfactorily display these excellent characteristics particularly when they are applied to color-print papers.
However, the dyes formed of the above-mentioned pyrazolotriazole type magenta couplers have had such a defect that the light-fastness thereof is relatively deteriorated.
Therefore, a variety of pyrazolotriazole type magenta couplers having a high light-fastness have been proposed. Among these proposals, the coupler proposed in Japanese Patent O.P.I. Publication No. 189537-1986 was found to be particularly excellent in light-fastness, that is, the coupler in which the carbon atom of a secondary or tertiary alkyl is bonded to the pyrazoloazole mother nucleus thereof.
It was, however, fount that this type of couplers have a defect that the gradation in the toe portion is softer than those of other pyrazolotriazole type couplers.
Therefore, when this type of couplers are applied to a color light-sensitive material, the gradation among the three layers, red-, green- and blue-light sensitive layers, become unbalanced and, in particular, magenta color is liable to be loud in high-light portions. In a light-sensitive material for color print, therefore, the so-called pink highlight phenomenon occurs, for example, sky or cloud becomes pinkish and snow does not come out in white but in pink. Human eye discriminates such a delicate phenomenal variation as mentioned above particularly in a low density to judge that a color print is not well-finished due to the phenomenon.
Accordingly, when designing a color light-sensitive material, much efforts have been directed to balance the gradation among the three layers particularly in their low density portions.
The gradation in the toe portion is softened by the pyrazolotriazole type coupler bonded to the above-mentioned carbon atom of secondary of tertiary alkyl. This phenomenon seriously degrades the commercial value of a light-sensitive material with the tendency of a pink highlight occurrence. It is not too much to say that this phenomenon leads the light-sensitive material to a fatal defect.
There have so far been varieous studies on the methods for controlling the gradation of silver halide photographic light-sensitive materials.
The methods which have been generally used include, for example, a method of suitably varying both the amounts of silver halides and couplers to be coated and the quantitative proportion of the silver halides to the couplers; the methods of making a mixture of two or more kinds of silver halide emulsions which are different from each other both in grains sizes and sensitization processes, of which are described in, for example, Japanese Patent O.P.I. Publication Nos. 71320-1975, 44016-1978, 78831-1981, 58137-1982, 150841-1982, 178235-1982, 14829-1983, and so forth; a method in which the conditions, additives and so forth are so selected as to harden the gradation in the toe portion when silver halide grains are chemically sensitized or color sensitized; a method in which a water-soluble rhodium salt is added in the process of forming silver halide grains described in, for example, Japanese Patent O.P.I. Nos. 11029-1977, 18310/1977, British Pat. No. 1535016 U.S. Pat. No. 3,448,709; and so forth. In these methods, however, there may be some instances where not only the toe portion is purposively hardened but also the gradation in the shoulder portion is hardened, where the gradation may be softened in long preservation, or where other photographic characteristics such as sensitivity, fogginess, exposure characteristics and so forth may be affected. Therefore, in the state of things, no effective technology was found out of the conventional technologies to harden only the gradation in toe portion but not to affect other characteristics.
Particularly, among the above-mentioned hardening methods applied to a pyrazolotriazole type coupler to which the carbon atom of the aforementioned secondary or tertiary alkyl is bonded, a method capable of displaying a substantial hardening effect in the toe portion has a tendency of deteriorating light resistance, while a method capable of reducing the deterioration of light resistance has a tendency of displaying a little hardening effect. It has not been easy to achieve both of the deterioration prevention of light resistance and the hardening effect in toe portion.
After the inventors have continued to try to solve the above-mentioned problems, they have discovered a method in which both of the light resistance and the gradation in toe portion can particularly be excellent by combining a specific hardening agent with a coupler having a specific structure selected from the pyrazoloazole type couplers to which the carbon atom of secondary or tertiary alkyl is bonded, so that they have achieved this invention.